The purpose of this investigation is to understand the mechanisms that control the abnormal transition of skin microvascular endothelial cells to the proliferating spindle-shaped cells present in lesions of AIDS- associated Kaposi's sarcoma. Under homeostatic growth conditions, skin microvascular endothelial cells in cell culture maintain a typical epithelioid configuration and display several of the unique features of endothelial cells observed in vivo (e.g., Weibel-Palade bodies, Factor VIII antigen, responsiveness to vasoactive amines, synthesis of Type IV collagen). When nuclear protein kinase C is activated by inflammatory cytokines, epithelioid endothelial cells rapidly convert to a spindle-shaped configuration and lose their specific endothelial cell markers. We will use our information on the lymphokines and second messengers that control normal skin microvascular physiology to determine if these factors function abnormally in KS and result in the increased rate of conversion to and proliferation of spindle-shaped endothelial cells in KS. We will: 1) isolate both normal and spindle-shaped cells from KS lesions; 2) determine the growth response of KS cells to the major lymphokines altered in AIDS-associated KS; 3) characterize the nuclear and cytoplasmic protein kinases activated in spindle-shaped KS cells; 4) identify the changes in gene expression in KS cells using CDNA expression libraries; and 5) determine the role of the tat gene in the regulation of the growth of KS cells. The information to be provided in this proposal should identify the basic defects in the formation of the spindle-shaped KS cells in immunocompromised subjects, and provide a more detailed understanding of the factors that control microvascular function in both normal and diseased skin.